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Y1 - Pathology > 3_Cell Bio I > Flashcards

3_Cell Bio I Flashcards

1
Q

how much of the genome binds proteins/ or affects gene expression?

(how large is the genome itself?)

A

80% of the genome either binds proteins, or affects gene expression;

human genome: 6.4 x 10^9 bases

20,000 genes encode proteins

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2
Q

difference b/w heterochromatin and euchromatin?

A

heterochromatin: transcriptionally INACTIVE

euchromatin: transcriptionally active; dispersed; “loosely packed”

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3
Q

review structure of DNA

A
  • “beads-on-a-string” form of chromatin;
  • nucleosome: inc. 200 nucleotide pairs of DNA; core histone and linker DNA
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4
Q

nuclease vs. exonuclease functions

A
  • nuclease: capable of cleaving the phosphodiester bonds between nucleotides of nucleic acids.
  • exonuclease: removes successive nucleotides from the end of a polynucleotide molecule.
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5
Q

what allows DNA double-helix to dissociate from histone core?

A

high concentration of salt

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6
Q

which parts of the DNA are NON-CODING?

A
  • Enhancer regions
  • Promoter region (binding sites for transcription factors)
  • Binding sites for proteins that maintain protein structure
  • Noncoding regulatory RNAs
  • Transposons (mobile genetic elements)
  • Specialized structural regions (telomeres, centromeres)
  • Role of 5-methylcytosine in silencing of gene expression
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7
Q

process from DNA –> protein

A
  1. DNA undergoes TRANSCRIPTION to form
  2. pre-mRNA –> undergoes SPLICING to remove introns (noncoding)–>
  3. mRNA which contains 5’-UTR and coding region (exons), and 3’-UTR –>
  4. undergoes TRANSLATION –> form protein
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8
Q

DNA polymorphisms:

define, types

A
  • def: DNA variations; sequence difference compared to reference standard (of 1-2% of population)
    • can be assoc. w/ risk factors for disease
  • types:
    • SINGLE NUCLEOTIDE POLYMORPHISM (SNP): 1% in coding regions; wide variability among populations
    • COPY NUMBER VARIATIONS (CNVs): 50% in coding regions; 5-24 x 10^6 base pair difference b/w individuals
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9
Q

what are the two categories for non-coding RNAs?

A
  • micro-RNAs (miRNAs)
  • long noncoding RNA (lncRNA)
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10
Q

micro-RNAs (miRNAs)

define, fxn, characteristics

A
  • def: non-coding RNA
  • fxn: involved in post-transcriptional SILENCING of expressed genes
  • KC:
    • processing –> RNA-induced Silencing Complex
    • presence of constant “seed sequence” in 3’-UTR
    • about 1,000 genes for miRNAs per genome
    • experimental use in “knockouts” of gene expression
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11
Q

long noncoding RNA (lncRNA:

define, fxn, characteristics

A
  • def: non-coding RNA; large number, at least 1 order of magnitude greater than coding RNAs
  • fxn:
    • modulation of gene expression,
    • involved in increased transcription;
    • role in gene silencing on X chromosome
  • kc: presence in telomeres at ends of chromosomes
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12
Q

which modified base is associated w/ silencing of gene expression?

A

in situ;

5-methylcytosine

  • (a methylated form of cytosine –>involved in regulation of gene transcription;*
  • When cytosine is methylated, the DNA maintains the same sequence, but the expression of methylated genes can be altered)*
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13
Q

histones:

structure; fxn; modification; other names

A
  • structure: low molecular weight proteins w/ nucleosomal DNA wrapped around it
  • fxn: regulation of gene expression
  • mod: by methylation, acetylation, phosphorylation
  • aka:
    • chromatin “writers”, “erasers”, “readers”
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14
Q

what are the various housekeeping fxns of the cell?

A
  • acquire nutrients
  • communication (intra- and inter-cellularly)
  • generate energy
  • protect from environment
  • molecular catabolism
  • movement
  • removal of senescent molecules
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15
Q

how are the various housekeeping fxns of the cells ORGANIZED?

A

COMPARTMENTALIZED w/in specific specialized ORGANELLES

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16
Q

PLASMA MEMBRANE:

structure and fxn

A
  • struc: double lipid layers
    • outer: glycolipids & sphingomyelins
    • inner: phosphatidylSERINE & phosphatidylinositol
    • most proteins are transmembrane; can form large complexes
  • fxn:
    • protect from environment
    • acquire nutrients
17
Q

which lipids are found in the OUTER layer of the plasma membrane?

A

outer: glycolipids & sphingomyelins

inner: phosphatidylSERINE & phosphatidylinositol

18
Q

glycocalyx:

define, location/ & fxn

A
  • def: carbohydrate-enriched coating w/ polysaccharide chains
  • loc: covers the extracellular surface of many cells, along w/ glycoproteins
  • fxn:
    • cell-cell interactions
    • cell-matrix interactions
    • chem barrier (protection)
    • mech barrier (protection)
19
Q

types of transport through plasma membrane?

A
  • passive diffusion: for small, nonpolar molecules
  • aquaporins: water moves by osmosis
  • passive/active transport mechanisms: for ions; bc lipid bilayers are impervious to ions
  • channel (carrier) proteins: low molecular weight molecules; specific transporters;
20
Q

channel (carrier) proteins:

fxn, mechanism

A
  • fxn: transport low molecular weight (<1000 d) molecules; specific transporter per molecule type; found in plasma membrane
  • mech:
    1. carrier protein binds solute
    2. conformational changes of carrier protein to make hydrophilic pore
    3. ligand can transport through
21
Q

active vs. passive transport

A
  • active: powered by ATPase
  • passive: uses potential electrical difference across plasma membrane
22
Q

endocytosis:

define, and types

A
  • def: receptor-mediated uptake of fluids/macromolecules
  • types:
    • small molecules: enter membrane invaginations (calveolae); invol. in folate transport and cell signaling; cAMP involved
    • large mol: enter via membrane invaginations (clathrin “basket” molecules)
    • receptor-mediated endocytosis (e.g. trans-ferritin, or low density lipoproteins)
23
Q

which size molecules use the following in endocytosis:

  • clathrin “basket” molecules?
  • calveolae
A
  • clathrin “basket” molecules = LARGE molecules
  • calveolae = small molecues
24
Q

exocytosis:

define, and types

A
  • def: EXPORT of molecules; packaged by RER and golgi –> form secretory vesicles
  • types
    • transcytosis: mvmt of vesicles b/w diff’t parts of the cell; transference of proteins across epithelia
    • pinocytosis:“pinching off” of membrane to form vesicle; clathrin involvement
25
Q

cytoskeleton:

composition

A
  • ACTIN MICROFILAMENTS
    • G-actin (“globular”; free monomer)
    • F-actin (“filamentous”; linear polymer microfilament)
  • INTERMEDIATE FILAMENTS
    • great variety amongst diff’t cells
    • incl: laminins, vimentin, desmin, neurofilaments, glial fibrillary acidic proteins, cytokeratins
  • MICROFILAMENTS:
    • thick fibrils
    • ATP is involv. in movement
    • kinesins and dyneins
26
Q

cell-cell interactions:

(3 categories)

A
  • tight (occluding) junctions: high resistance barrier; proteins include zonulin, catenin, and occludin
  • desmosomes (anchoring) junctions: attach cells to other cells; proteins incl. cadherins, and integrins
  • communicating (gap) junctions: facilitate electrical or chemical signals b/w cells; connexin proteins
27
Q

connexon:

A

electrical or chemical connections b/w cells

28
Q

endoplasmic reticulum:

function, RER vs. SER

A
  • fxn: site of synthesis for all transmembrane proteins and lipids for organelles and all molecules exported from cells
  • RER: membrane-bound ribosomes translate mRNA into proteins
    • (protein synthesis in FREE ribosomes)
  • SER: involved in hormone synthesis
29
Q

golgi apparatus:

function; processes

A
  • fxn:
    • modification of proteins
    • glycosylation transport
  • processes:
    • proteins and lipids enter Golgi apparatus AFTER synthesis in RER
30
Q

lysosomes:

structure, function

A
  • structure:
    • membrane-bound; contain 40 acid hydrolases
    • recognizes mannose-linked proteins
  • function:
    • autophagy: isolates senescent proteins for transport to lysosomes, where hydrolysis ensues
    • phagocytosis: by neutrophils or macrophages results in a “phagosome”, after fusion w/ a lysosome
31
Q

proteasomes:

functions, mechanism

A
  • fxns: (waste disposal)
    • degrade denatured or misfolded proteins
  • mech:
    • tagged by a protein: “ubiquitin”
    • digest proteins into small peptides, which are subsequently degraded to individual amino acids
32
Q

mitochondria:

function; pathology

A
  • fxn:
    • contains DNA; maternally inherited
    • energy generation; drives mitochondrial protein pumps
    • thermogenin: generates heat
  • pathology:
    • mitochondrial genetic diseases may also be X-linked or autosomally inherited, due to sources of mitochondrial proteins
33
Q

mitochondria:

mechanism

A
  • intermediate metabolism; Krebs cycle
  • anaerobic glycolysis: by rapidly-growing cells (Warburg effect), w/ increased glucose and glutamine uptake
  • role in cell death: necrosis, failure of ATP generation; apoptosis, programmed cell suicide
34
Q

what is the structure of the MITOCHONDRIA

A

Y1 - Pathology (14 decks)

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